Clock ticking for Philippine hostages

Government troops have been combing Basilan for four days

ZAMBOANGA, Philippines - Philippine troops have shot dead two Muslim kidnappers on the eve of a deadline to behead three U.S. hostages.

Three other members of the Abu Sayyaf group were captured in the fighting on the outskirts of the provincial capital of Isabela on southern Basilan island, where the extremists hold the Americans and 10 Filipinos, the military said.

There were no reports of government casualties. The clash began after the rebels attacked an army detachment 14 kilometers (eight miles) from Isabela.

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The kidnappers, believed to be holding their hostages in another town on Basilan, have warned they will behead a U.S. missionary couple and an American tourist unless Manila meets their demand for a Malaysian to negotiate with them.

On Thursday, Abu Sayyaf leader Sabaya threatened to "chop the heads off the Americans in 72 hours" if Manila didn't appoint a Malaysian mediator who negotiated last year with Abu Sayyaf about the release of foreign hostages taken from a Malaysian resort, reportedly for millions of dollars in ransom.

President Gloria Macapagal Arroyo has rejected the demand for a foreign negotiator, vowing to continue the military operations.

She said the government has already designated a local intermediary to talk to the kidnappers.

"We need a news blackout. We have to sanitize the news that is coming out," Arroyo said in a radio interview on Sunday when asked about the hostage drama.

It has been four days since thousands of government troops started combing the southern island of Basilan, racing against the deadline.

Besides a few telephone calls from Sabaya in recent days, mostly cut off after a brief, shaky connection, government negotiators reported little contact with the group.

Manila has vowed it will not pay ransom to the Abu Sayyaf, whose members are estimated to number some 1,100 fighters in southern Philippines, and will only discuss the hostages' unconditional release.

Explosion

Late Saturday, a grenade explosion in the city of Zamboanga -- a brief boat ride from Basilan island where the hostages are held -- drew a rapid reaction from soldiers backed by a tank.

The military have had little contact with the kidnappers in recent days

Authorities said the explosion was sparked from a civil dispute. After decades of insurgency, the area is rife with cheap weapons and hand grenades.

Meanwhile, three FBI agents arrived in the southern city of Zamboanga on Saturday to discuss the hostage crisis with local police and military officials.

The U.S. Embassy said the agents are only offering technical advice and are not participating in the hostage hunt.

The Abu Sayyaf seized Americans Guillermo Sobero and missionaries Martin and Gracia Burnham on May 27 in a raid on a western Philippine beach resort.

They also took 17 other hostages, including three resort workers. Nine hostages escaped during fierce fighting with the military a week ago. Two resort workers were later found hacked to death. One of them was beheaded.

After seizing four people from a hospital last Saturday, suspected to be used to treat wounded comrades, the Abu Sayyaf now has 13 hostages.

The Abu Sayyaf has repeatedly vowed to kill foreign hostages in the past but has not carried out the threat.

The Associated Press contributed to this report.